A novel NO/sub 2/ gas sensor based on bis[phthalocyaninato] samarium complex/silicon hybrid charge-flow transistor

Abstract

A new kind of sandwich-like bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] samarium complex Sm[Pc ] 2 (Pc = Pc(OC 8 H 17 ) 8 ) is used as film-forming material. Pure Sm[Pc ] 2 and mixture of Sm[Pc ] 2 and octadecanol(OA) deposited from both pure water and 10 4 M Cd 2+ subphases are investigated. It is found that a mixture of 1:3 Sm[Pc ] 2 :OA forms an excellent material for the fabrication of the gas-sensing Langmuir-Blodgett (LB) film by studying the film-forming characteristics. A new gas sensor has been fabricated by incorporating the multilayer LB film into the gate electrode of a metal-oxide-semiconductor field effect transistor, forming an array of charge-flow transistor. On the application of a gate voltage (V GS ), greater than the threshold voltage (V TH ), a delay was observed in the response of the drain current. This is due to the time taken for the resistive gas-sensing film to charge up to V GS . This delay characteristic was found to depend on the concentration of NO 2 . Results are presented showing that the device can detect reversibly the concentration of NO 2 gas down to 5 ppm at room temperature. Index Terms-Bis[phthalocyaninato] samarium complex, charge-flow transistor (CFT), gas sensor, Langmuir-Blodgett (LB) film, metal-oxide-semiconductor field effect transistor (MOSFET), nitrogen dioxide.

Design and application of a metal wet-etching post-process for the improvement of CMOS-MEMS capacitive sensors

“…Cross-sectional view of the CMOS-MEMS gap-closing capacitive sensors with in-plane and out-of-plane sensing electrodes. [1][2][3]5]. These dry-etching processes can provide clean and directional structure geometry.…”

“…CMOS-MEMS capacitive sensors have been widely used to detect the changes of various physical quantities such as acceleration [1][2][3], humidity [4], angular rate [5], etc. Presently, many studies are being reported to improve the performance of capacitive-type CMOS-MEMS sensors.…”

Modeling the Microstructure Curvature of Boron-Doped Silicon in Bulk Micromachined Accelerometer

“…However, with the increasing demand for microdevices with high sensitivity and high performance, bulk micromachining has been developed to create microstructures with thick layers similar to those achieved by the bulk silicon-dissolved wafer process, based on the self-stopped etch technique of heavy boron-doped silicon [6]. This fabrication technology is widely used to make microaccelerometers [7,8], microgyroscopes [9,10], microswitches [11,12], and microgears [13]. This technology also exhibits curvature behavior because its boron-doping mechanism is the same as that used in surface micromachining [5].…”

Use of the electrochromic behaviour of lanthanide phthalocyanine films for nicotinamide adenine dinucleotide detection

“…UV-visible spectra of thin films of bisphthalocyanines are susceptible to the exposure of electron donor and electron acceptor gases. Langmuir-Blodgett films of erbium bis[octakis(octyloxy)phthalocyaninato] complex were exploited for use in different types of room temperature conductometric NO 2 sensors (Xie et al 2001(Xie et al , 2003. The exposure of LuPc 2 to NO x caused the shift of the Q-band to a higher wavelength, leading a change in the film colour from green to red.…”